Process for producing oxalic acid.



UNITED STATES PATENT OFFICE.

EMIL Von PORTHEIM; OF PRAGUE-SMICHOW, AUSTRIA-HUNGARY.

PROCESS FOR PRODUCING OXALIC ACE).

No Drawing.

To all whom it may concern:

Be it known that I, EMIL VON PORTHEIM, manufacturer, being a subject ofthe. Emperor of Austria-Hungary, residing at Prague-Smichow, in Bohemia,Austria- Hungary, have invented certain new and useful Improvements inProcesses for Producing Oxalic Acid; and I do hereby declare thefollowing to be a full, clear, and exact description of the invention,such as will enable others skilled in the art to which it appertains tomake and use the same.

' The process for producing oxalic acid from carbohydrates by meansofnitric acid (with or without the presence of a catalyzer) hitherto inuse, brings the reaction down to a state in which the nitric acid israrefied to such an extent by giving on oxygen and nitrous gases, as torender it unable to oxidize the c'arbohydrates. When the reaction hasthus become stationary, the solution subjected to reaction stillcontains nitric abid of about 20-30%, the remaining carbohydrates, theintermediary products of oxidation of these latter, and the catalyzeremployed, and it will be found to e saturated with oxalic acid aftertheorystallized oxalic acid has been filtered out. The said solution isso valuable as to render its utilization of the greatest possibleimportance for the commercial significanceof the process.

To this end various means have been tried -.to compensate for therarefaction of the re- 35.

action solution with the view to obtaining a continuation of thereaction process. Thus it has been suggested to concentrate the solutionin 'vacuo. This however cannot be done without oxidizing, to a largeextent, the carbohydrate and the oxalic acid into carbonic acid. Furtherthe attempt has been made to raise the concentration of the nitric acidin the reaction solution again to its .original point by adding to thesolution a highly concentrated nitric acid. But in consideration ofthe'fact that the nitrous gases, arising from the reaction, wereconverted in towers in the known manner, into nitric acid of only about52%, it was necessary to con centrate this said 52% nitric acid up to94%, which as is well known, proves very expensive. Notwithstanding,even an acid concentrated to amaximum degree will add water to thereaction solution, for even a;

nitric acid concentrated to the technically highest degree possiblewill, on its decompo- Speciflcation of Letters Patent.

Application filed October 3, 1914. Serial No. 864,882.

Patented Oct. 19, 1915.

sition, yield a quantity of water equal to 20% of its own. weight as aresult of the oxidizing action. Thesuggestion to work the reactionsolution up by the aid of bases, proved still less practicable.

We have now found that a continuous Working with one and the samesolution is possible if nitrogen peroxid (N0 or N .O is added to thereaction solution in the place of nitric acid. This said nitrogenperoxid may suitably be obtained by oxidation with air or oxygen fromthenitrous gases arising during the reaction, and may then be separatedout, say by liquefaction, from the remaining portion of the air. Thenitrogen peroxid may be introduced into the reaction either in a. liquidor gaseous state. In the former case, it settles below the reactionsolution and slowly dissolves within the same.

However, the nitrogen peroxid may likewise be introduced from anexternal source of supply, for example, from reaction vessels in whichthe same reaction process is being carried .out by means of nitric acid(this of course after the admission of air), or from reactions of awholly diiferent description. In this case itisunnecessary to employconcentrated nitric acid, the reaction will prove successful, ifthestarting preparation be an aqueous solution of sugar or a solution ofsugar contained in rarefied nitric acid.

. By these means the possibility is given of proceeding with thereaction without altering the degree of concentration of the reactionsolution. All that need be done is to add nitrogen peroxid and freshquantities of carbohydrates, and to remove from time to time the oxalicacid which has formed. In the place of these saidsolu-tions it is alsopossible to work with an addition of glacial acetic acid or any otherabsorbents for the nitrogen peroxid or even without any solventaltogether.

The nitrous gases act as a carrier for the oxygen (say of the air) ontothe carbohytallization.

afresh to the solution, whereupon the reaction may begin again. Theoxalic acld which has been filtered is purified by re-crys- Example II:Into a solution'of 100 parts by weight of sugar and 0.2 parts by weightof vanadic acid contained in 150 parts by weight OfIiitllC acid of adensity of 1.2 there are introduced the nitrous gases escaping from asecond reaction vessel and which are oxidized by the admixture with air,after the oxidation has been carried through, the gases are freed fromany excess of air in the known manner by introducing them intoconcentrated sulfuric acid and then re-expeling the nitrous gases.Within a short space of time the formation of oxalic acid commences andsimultaneously with it the development of the lower nitric oxids, whichlatter are re-oxidized and passed on into a. third preparing vessel.

As soonas the development of the nitric 'oxids obtained from onereaction (being the one first set out with) begins to slacken to any'considerabledegree, the vessel 1s re- 'moved from the cycle, thecontents are filtered, and sugar is again added to the mother liquor,whereupon the vessel is re-in'troduced into the cycle as the last of theseries.

Example III: A flow of nitrogen peroxid,

in some cases mixed with air, is passed through a solution of 100 partsby weight of sugar, 2 parts by weight of oxid of molyb denum and 100parts b weight of water. Whenthe solution is rep ete with crystals it isfiltered, sugar is again added to the filtrate (say about as much as hasbeen used up) and nitrogen peroxid is introduced afresh. Example IV:'100 parts by weight of sugar are mixed with 0.2 parts by weight ofvanadic acid, spread in a thin coat on.

hurdles and subjected to the action of nitrogen peroxidr The sugar willthen be gradually converted into oxalic acid.

I claim' 1. The process of producing oxalic acid from a solution ofcarbo-hydrates in the presence of nitric acid and'a catalyzer, whichcomprises oxidizing the nitrogen oxid gas escaping during the reactionand introducing such oxidized gas into the solution.

2. The process of producing oxalic acid ence of a catalyzer, which"comprises introducing peroxid of nitrogen (N0 into the solution. I

3. The process of producing oxalic acid from a solution of'carbohydratein the presfrom a solution containing carbohydrate and acatalyzer in the presence of nitric acid, which comprises introducinginto the mixture a higher oxid of nitrogen.-

In testimony that I claim the foregoing as 'myinvention, I have signedmy name in presence of two subscribing witnesses.

Witnesses:

JOHANN BARBA, C. FISCHER.

EMIL VON PORTHEIM. p

